1. Field of the Invention
The present invention generally relates to a plasma display panel, more particularly to a plasma display panel capable of: dividing one screen of the plasma display panel into a plurality of smaller screens, the plurality of smaller screens operating independently at the same time, whereby each panel cell keeps a state of stable discharge; and decreasing the sharing data of working circuits, whereby it is possible to design circuits with common electronic devices so that it is cheaper to manufacture and easy to design circuits.
2. Description of the Related Art
As shown in FIG. 1, an electrode array of a general three-electrode surface-discharge Plasma Display Panel includes scanning electrodes 2 where a scanning pulse is applied during an address period, common electrodes 3 where a sustaining pulse is applied in order to sustain discharge state, and data electrodes 1 where a data pulse is applied in order to generate sustaining discharge between selected scanning electrodes 2 and the common electrodes 3. A cell 5 is formed at each intersection where a vertical electrode, one pair of the scanning electrodes 2, and the common electrodes 3 intersect with a horizontal electrode and data electrodes 1. The plasma display panel is formed by the aggregation of such a plurality of cells.
FIG. 4 is a partial sectional view of a plasma display panel.
Referring to FIG. 4, a discharge space 20 is formed between barrier ribs 16 which support a horizontal electrode 14 and a vertical electrode 19. Phosphor 17 is formed over the vertical electrode 19. Reference numerals 12 and 13 designate substrates, and reference numerals 15 and 18 designate insulating layers.
FIG. 2 is a timing chart of signals to operate the plasma display panel. A sustaining pulse 7 is applied to the common electrodes 3 of Cl-Cn. A sustaining pulse 8 having the same cycle as the sustaining pulse 7 is also applied to the scanning electrodes 2 of Sl-Sn, but it has different timing from the pulse of the common electrodes 3.
A scanning pulse 10 and an extinguishing pulse 9 are also supplied to respective scanning electrodes. A data pulse 11 is applied to data electrodes of Dl-Dn at the same time as the scanning pulse is applied to the scanning electrodes.
In order to light the cell 5 where the scanning electrodes 2 intersect with the data electrodes 1, a data pulse 11 synchronized with the scanning pulse 10 applied to the scanning electrode 2 should be supplied to the data electrodes 1. As a result, discharge occurs at the cell 5 and is maintained by the sustaining pulses 7 and 8 which are supplied to the common electrode 3 and the scanning electrodes 2, and it is completed by an extinguishing pulse 9.
In a method operating one screen as shown in FIG. 1 using a single operating circuit, a pulse width for operating respective cells of the plasma display panel varies with respective cell properties. A general scanning pulse, however, has the width of around 2.5 .mu.s. As shown in FIG. 2, since there should be provided a time interval in order that one scanning pulse 11 and two sustaining pulses (7+8) can be applied in one sustaining period. A possible minimum period of the sustaining pulse is 5.5 .mu.s, which is calculated as follows: EQU 2.5 .mu.s (width of the scanning pulse 10)+1.5 .mu.s (width of the sustaining pulse 7)+1.5 .mu.s (width of the sustaining pulse 8)=5.5 .mu.s(1)
This time is also a period of a data pulse required for applying a data pulse to the scanning electrodes on a next scanning line after the data pulse has been applied to scanning electrodes on one scanning line.
It takes 1/60 second in scanning one field in a NTSC television signal of an interlaced scanning method.
When the number of the scanning electrodes 2 of a plasma display panel is given to N, since one field in a 256 gray scale is composed of eight subfields, an interlaced scanning mode should satisfy the equation below: EQU 5.5 .mu.s.times.N/2.times.NfS.ltoreq.1/60 sec (2)
wherein N is the number of the scanning electrodes, and NfS is the number of subfields making one field.
From the above equation (2), when eight subfields make one field, in other words, NfS=8, the allowable maximum number of the scanning electrodes becomes 757.
A plasma display panel, one of the flat display devices is developed as a large size wall-hanging display device because it is easy to achieve a large picture display size in its aspects of panel structure. One problem in fabricating and operating a large-sized screen display device is that more pixels have to be given to one screen according to the increase in screen size. The increase in the number of pixels means the increase in a data amount to be processed in one frame. A flat display device for a high definition television has to satisfy the requirements of having 256 gray levels and a resolution of 1280.times.1024 and higher. In order to satisfy the above requirements, a vast data amount of about one gigabit per second must be processed.
The periods of the data pulse and the sustaining pulse to satisfy the resolution of 1280.times.1024 can be obtained from equation (2), and the equation (3) below comes out. EQU Ts1.ltoreq.1/60 sec.div.N/2.div.8 (3)
Thus, in order to operate a large size television having 1024 horizontal electrodes, the period of the sustaining pulse has to satisfy the equation Ts1&lt;4 .mu.s.
In order to decrease the period of the sustaining pulse, the turn-on time of cells in a display panel has to be decreased. When the decrease in the widths of the sustaining pulse and the scanning pulse is excessive, the discharge state of cells of the plasma display panel becomes unstable. Thus, it is impossible to decrease the pulse width below a certain time required for the discharge. This limits the number of electrodes which can be operated at the same time and acts as an important limitation in making a large size display device.
In addition, a high speed electronic device made of GaAs should be used in order to process a large amount of data such as one gigabit. In case the electronic device is used, the cost of driving circuits is high, which is a problem in the plasma display panel business.
Another hindrance in designing the driving circuit is a response time of the driving circuit. In order to operate the plasma display panel by a subfield method, eight bits of data have to be stored in a field memory and then the same weight bits have to be sequentially transferred to a serial to parallel converter (SPC) one by one.
When the pixel number of the plasma display panel is M.times.N, a data amount of M.times.N.times.8 should be transferred to the SPC during one field. Therefore, the time Td1 required for transferring one bit is defined by equation (4) below: EQU M.times.N/2.times.8.times.Td1&lt;1/60 sec (4)
Accordingly, the time Tdl is obtained from the substitution of M=1280 and N=1024 in equation (4) and comes out about 3.2 nsec. SPC can be made using a flip flop. In considering that Td1 of a flip flop in common use is approximately 8 nsec, a SPC has to be specifically designed using a GaAs device which is 2.5 times faster than the flip flop in common use.
However, the GaAs device is very expensive compared to a common electronic device, so it is difficult to design an inexpensive operating circuit by using the GaAs device.